Flocculated microbial inoculants for delivery of agriculturally beneficial microorganisms

Abstract

PCT No. PCT/US94/01997 Sec. 371 Date Jun. 5, 1995 Sec. 102(e) Date Jun. 5, 1995 PCT Filed Feb. 24, 1994 PCT Pub. No. WO94/19924 PCT Pub. Date Sep. 15, 1994Flocculated bacterial cells are utilized as high-density crop inoculants and delivery systems for one or more agriculturally beneficial microorganisms. The flocculated form of bacteria, such as Azospirillum and Rhizobium, possess superior survivability under storage, as a seed coating and mixed seed priming media. Other microorganisms may be co-flocculated with the aforementioned bacteria, thereby providing a crop inoculant for delivery of multiple agriculturally beneficial microorganisms.

What is claimed is: 
     
       1. A method of delivering microorganisms to a plant to improve plant productivity, which comprises inoculating a plant component under agronomical conditions with a preformed co-floc comprising a combination of Azospirillum spp. and Rhizobium spp., said plant component being selected from the group consisting of seeds, stems, roots, flowers and leaves. 
     
     
       2. A method of preparing a mixture comprising a seed and microbial inoculant mixture for beneficial augmentation of plant growth, said inoculant including a co-flocculent of Azospirillum spp. and Rhizobium spp., said method comprising the steps of: a) providing a flocculation medium comprising mineral salts and organic acids necessary for growth of said Azospirillum spp. and Rhizobium spp., a carbon source and a nitrogen source, the ratio of carbon to nitrogen in said flocculation medium being at least 30:1;   b) culturing said Azospirillum spp. and Rhizobium spp. in said flocculation medium under conditions promoting growth and flocculation of said Azospirillum spp. and Rhizobium spp., thereby producing a co-floc comprising Azospirillum spp. and Rhizobium spp.;   c) harvesting said co-floc: and   d) mixing said co-floc with said seed, thereby producing a mixture of seed and microbial inoculant comprising a flocculated form of said Azospirillum spp. and Rhizobium spp.   
     
     
       3. A method as claimed in claim 1, wherein inoculation is effectuated by admixture of said co-floc with seeds. 
     
     
       4. A method as claimed in claim 1, wherein inoculation is effectuated by spraying said co-floc on said plant components. 
     
     
       5. A method as claimed in claim 1, wherein inoculation is effectuated by admixture of said co-floc with germination media. 
     
     
       6. A method as claimed in claim 1, wherein inoculation is effectuated by admixture of said co-floc with soil. 
     
     
       7. A microbial inoculant for a plant, which comprises a co-floc comprising a combination of Azospirillum spp. and Rhizobium spp. 
     
     
       8. A microbial inoculant as claimed in claim 7, further comprising at least one additional agriculturally beneficial microorganism selected from the group consisting of Enterobacter spp., Bacillus spp., and Pseudomonas spp. 
     
     
       9. A microbial inoculant for a plant which comprises Azospirillum spp. coflocculated with an additional microorganism selected from the group consisting of Enterobacter spp., Pseudomonas spp., and Bacillus spp. 
     
     
       10. A microbial inoculant for a plant which comprises Rhizobium spp. co-flocculated with an additional microorganism selected from the group consisting of Enterobacter spp., Pseudomonas spp., and Bacillus spp. 
     
     
       11. A method of preparing a co-flocculated microbial inoculant for a plant, the microorganism constituents of said inoculant comprising a co-floc of Azospirillum spp. and Rhizobium spp., said method comprising the steps of: a) providing a flocculation medium comprising mineral salts and organic acids necessary for growth of said flocculating microorganisms, and a carbon source and a nitrogen source, the ratio of carbon to nitrogen in said flocculation medium being at least 30:1;   b) culturing said flocculating microorganisms in said flocculation medium under conditions promoting growth and flocculation of said microorganisms thereby producing a co-floc comprising said microorganisms; and   c) harvesting said co-floc, thereby producing a microbial inoculant comprising a flocculated form of said microorganisms.   
     
     
       12. A method as claimed in claim 11, wherein said flocculated Azospirillum spp. are selected from the group consisting of A. brasilense and A. lipoferum. 
     
     
       13. A method according to claim 11 wherein said co-floc further comprises an agriculturally beneficial microorganism selected from the group consisting of Enterobacter spp., Bacillus spp., and Pseudomonas spp. 
     
     
       14. A method as claimed in claim 11, wherein said flocculated Rhizobium spp. is R. leguminosarum biovar phaseoli. 
     
     
       15. A method as claimed in claim 2, said method further comprising including in said flocculation medium at least one microorganism selected from the group consisting of Enterobacter spp., Pseudomonas spp. and Bacillus spp. 
     
     
       16. A method as claimed in claim 2, said method further comprising adding at least one microorganism selected from the group consisting of Enterobacter spp., Pseudomonas spp. and Bacillus spp. to said co-floc, thereby forming a mixed floc.